1. Field of the Invention
This invention relates to production of .alpha.-olefin polymers, and more particularly it relates to a process for producing highly crystalline .alpha.-olefin polymers having a good particle form, with a high yield, by the use of a preliminarily activated catalyst which is suitable for polymerization of .alpha.-olefins, particularly gas phase polymerization, and further, as a modification of gas phase polymerization, a combination of gas phase polymerization with slurry or bulk polymerization.
2. Description of the Prior Art
The inventors of the present application have developed processes for polymerizing ethylene or .alpha.-olefins containing ethylene, by the use of catalysts comprising a combination of an organoaluminum, etc. with a solid product (which will be hereinafter referred to as solid catalyst component) obtained by having a transition metal compound supported on a solid product (I) obtained by reacting a trivalent metal halide with a divalent metal compound, in the following various reaction manners.
For examples, the following processes have been proposed:
(1) a process wherein a transition metal compound is reacted with the above-mentioned solid product (I) in the presence of an aromatic compound (Japanese patent publication Nos. 13,609/1972 and 16,782/1974); PA0 (2) a process wherein the above-mentioned solid product (I) is reacted with a polysiloxane or an electron donor, and thereafter with a transition metal compound (Japanese patent publication No. 13,827/1977; Japanese patent application laid-open No. 61,283/1979); PA0 (3) a process wherein a polysiloxane or an electron donor and a transition metal compound are added at the same time or a complex of them is added to the above-mentioned solid product (I), to effect reaction (Japanese patent application laid-open Nos. 116,078/1979, 113,687/1979 and 124,091/1979); PA0 (4) a process wherein either one or both of at least one kind of electron donors and at least one kind of electron acceptors are reacted with the above-mentioned solid product (I), in a plurality of divided portions (Japanese patent application No. 101,960/1978); PA0 (5) a process wherein at least one kind of electron donors and at least one kind of electron acceptors are reacted with the above-mentioned solid product (I), and at that time, TiCl.sub.4 is employed as an electron acceptor at least once, and further the resulting solid catalyst component, an organoaluminum compound and an electron donor are combined together (Japanese patent application No. 106,797/1978); PA0 (6) a process wherein various additives such as titanium alkoxides, silicone oils, polyethylene glycol dialkyl ethers, other electron donors, etc. are added at the time of polymerization (Japanese patent publication Nos. 13,609/1972, 13,772/1972). The inventions of these processes (1) to (6) will be hereinafter referred to as prior inventions. PA0 (A) Trivalent metal halide PA0 (B) Divalent metal compound (hydroxide, oxide or carbonate or divalent metals or composite salt containing the foregoing compounds or hydrate containing divalent metal(s)). PA0 (ED) Electron donor PA0 (EA) Electron acceptor PA0 (OAl) Organoaluminum compound (.alpha.-O) .alpha.-Olefin PA0 (1) a manner wherein (OAl), the solid product (II) and (ED) are mixed together and thereafter (.alpha.-0) is added for preactivation; (2) a manner wherein the solid product (II), (OAl) and (ED) are added in an optional order in the presence of (.alpha.-0); (3) a manner wherein the solid product (II) and (OAl) are mixed together and thereafter (.alpha.-0) is added, followed by further adding (ED); (4) a manner wherein the solid product (II), (OAl) and (ED.sub.1) are mixed together in an optional order, and thereafter (.alpha.-0) is added, followed by further adding (ED.sub.2) ((ED.sub.1) and (ED.sub.2) may be the same or different); and (5) (OAl) and the solid product (II) are mixed together or the solid product (II), (OAl) and (ED.sub.1) are added in an optional order, followed by adding an .alpha.-olefin of a first kind (.alpha.-O.sub.1), thereafter further adding (ED.sub.2) and again adding an .alpha.-olefin of a second olefin (.alpha.-O.sub.2) ((ED.sub.1) and (ED.sub.2) and (.alpha.-O.sub.1) and (.alpha.-O.sub.2) may be the same or different, respectively). In any of these manners, when the solid product (II), (OAl) and (.alpha.-O) have been brought into a coexistent state, polymerization treatment is to be carried out.
In case where these prior inventions are applied to slurry polymerization or bulk polymerization, various advantages are brought about such that polymer yield per unit weight of catalyst component is very high; crystallinity of polymers of .alpha.-olefins such as propylene is high; particle form of polymers is good, particularly in the case of the inventions of the processes (5) to (6), it is possible to control the molecular weight distribution into a narrower range; etc.
On the other hand, gas phase polymerization has advantages in that, recovery and reuse of solvents employed for polymerization as in the case of slurry polymerization process are unnecessary, and recovery and reuse of liquefied monomers e.g. liquified propylene as in the case of bulk polymerization process are also not carried out; hence the cost for solvent or monomer recovery is slight and it is possible to simplify the apparatus for producing .alpha.-olefin polymers. However, gas phase polymerization process has disadvantages in that since the monomer inside the polymerization vessel is present in gas phase, the monomer concentration is lower than those in the cases of slurry polymerization process and bulk polymerization process; hence the reaction rate is lower and the polymer yield per unit amount of catalyst is insufficient, and since the retention time is to be extended to increase the yield, as enlarged reaction must be used or since such a component as trialkylaluminum is employed in an excess amount for elevating the catalyst activity, the stereoregularity is thereby reduced. Gas phase polymerization process also has disadvantages in that since the catalyst particles are not uniform, the resulting polymer particles are also not uniform; during the polymerization, oligomerization occurs, polymer particles agglomerate, and the removal of polymerization heat is so insufficient that the polymer particles become more agglomerative and massive, which brings about clogging of the port through which the polymer particles are discharged out of the polymerization vessel, or clogging of the succeeding transportation line which in turn makes it difficult to carry out a long lasting stabilized continuous operation; and as to the quality of the polymer particles, these particles are rough and have a considerable dispersion in the quality due to the inferior dispersion of stabilizer as well as the considerable dispersion in the physical properties between the polymer particles.
The object of the present invention is to provide a process for producing high-quality .alpha.-olefin polymers with a higher yield in a long lasting stabilized manner even when the process is relied on gas phase polymerization process where the monomer concentration is relatively low.